The genetic regulation of liver microsomal CYP2E1 activity among strains of the viviparous fish Poeciliopsis

CYP2E1 expression was examined within, among, and in F 1 and backcross progeny of strains ( P. monacha S68-5; P. viriosa M65-23) of the viviparous fish Poeciliopsis. CYP 2E1 activity varied dramatically in P. monacha, and P. viriosa (3.9±0.8 and 9.6±1.3 μg/min/mg) as well as the temperature which gave maximal activity ( T 0=25°C and 31°C). F 1 individuals from a crosses between P. monacha and P. viriosa, produced progeny whose CYP2E1 activity segregated into three different groups: (1) phenotypically the same as P. viriosa; (2) intermediate between the two parental strains; and (3) phenotypically the same as P. monacha. When a male P. monacha was crossed with a female P. viriosa 25% of the offspring had an intermediate phenotype and 65% the maternal P. viriosa phenotype. From the same cross, 85% of the females progeny had the maternal phenotype, while 80% of male progeny had the intermediate and paternal phenotype, suggesting an effect of the maternal genome on the F 1 phenotype. Among F 1 fish the T 0 was evenly distributed between parental values. In the backcross of a F 1 female to a male P. viriosa, CZX-6-hydroxylase activity segregated into the same three phenotypes with 60% of the progeny expressing the P. monacha phenotype. From the same cross, 70% of females and 40% of males expressed the P. monacha phenotype. The T 0 in the backcross were evenly distributed between the two parental values and the sex ratio among progeny was different than expected.